Application Information SSC2001S Power Factor Correction Continuous Conduction Mode Controller General Description The SSC2001S is a continuous conduction mode (CCM) control IC for power factor correction (PFC). The IC allows the realization of high-power output, high-efficiency, and power management systems which require few external components by the average current control system. Features and Benefits • Continuous conduction mode (CCM) system: low peak current and suitability for high power applications • Average current control system: no multiplier and few external components allows simple circuit configuration because no input voltage detection required • PWM and frequency modulation functions: PWM operation frequency fixed at 65 kHz (typ) with superimposed variable frequency according to duty cycle • Maximum duty cycle 94% (typ) • Error amplifier reference voltage 3.5 V (typ) • Built-in high speed load response (HSR) function • Brown-in/brown-out protection function: protects the power supply at low input voltages • Protection functions: ▫ Output overvoltage protection (OVP): turns off gate output on pulse-by-pulse basis, with auto restart ▫ Overcurrent protection (OCP): two types, both with auto restart: – VIS(OCPL) : limits power by reducing duty cycle of next cycle after detection – VIS(OCPH) : turns off gate output on pulse-by-pulse basis ▫ Open loop detection (OLD) on output: stops oscillation, and the operation switches to standby mode; auto restart after removal of cause of open loop Figure 1. SSC2001S packages are industry-standard SOP8 surface mount. Applications Power factor correction of middle to high power for electronic devices such as: • AC/DC power supplies • Digital appliances for large size LCD/PDP television and so forth • Office automation (OA) equipment for computer, server, montior, and so forth • Communication facilities Table of Contents Specifications 2 Functional Block Diagram Pin-out Diagram and List Package Outline Drawing Package Diagram Absolute Maximum Ratings Electrical Characteristics Typical Application 2 2 3 3 4 5 7 Functional Description 8 Startup Operation Soft Start Function Continuous Conduction Mode (CCM) Operation Current Control (PFC Control) SSC2001S-AN, Rev.1.2 8 9 9 10 Voltage Control (Output Constant Voltage Control) High Speed Load Response (HSR) Frequency Modulation Gate Drive Protection Functions Brown-In / Brown-Out Overcurrent Protection (OCP) Output Overvoltage Protection (OVP) Output Open Loop Detection (OLD) Design Notes Inductor Design Parameters Peripheral Components PCB Trace Layout and Component Placement SANKEN ELECTRIC CO., LTD. 10 11 11 11 12 12 12 13 13 14 14 16 17 Functional Block Diagram 7 VCC Regulator Oscillator UVLO Gate Driver 8 GATE OLD Input Low Voltage Detection 3 IS Protection OCP(H) OVP OCP(H) OCP(L) 2 ICOMP PWM Logic PWM Logic Protection Input Low Voltage Detection 4 VINS 6 Ramp Generator Protection OLD PWM Logic OVP VFB Error Amplifier Current Amplifier HSR GND 1 5 GND VCOMP Pin List Table Pin-out Diagram GND 1 8 GATE ICOMP 2 7 VCC IS 3 6 VFB VINS 4 SSC2001S-AN, Rev.1.2 5 VCOMP Name 1 Number GND Ground Function 2 ICOMP Current amplifier output 3 IS 4 VINS 5 VCOMP 6 VFB Output constant voltage control signal/output overvoltage signal/output open loop detection signal input 7 VCC Control circuit power supply input 8 GATE Gate drive output Overcurrent detection signal input Input low voltage detection signal input (Brown-in/brown-out protection function) Error amplifier output/phase compensation SANKEN ELECTRIC CO., LTD. 2 Package Diagram SOP8 package 5.2 ±0.3 1 0.695 TYP 6.2 ±0.3 5 4.4 ±0.2 8 4 0 to 10° 0.05 ±0.05 1.27±0.05 0.10 0.12 M +0.1 0.15 –0.05 1.5 ±0.1 5.25 ±0.3 0.4±0.2 0.4±0.1 Unit： mm SC2001 SK YMD XXXX Pb-free. Device composition compliant with the RoHS directive. SSC2001S-AN, Rev.1.2 Part Number Lot Number Y is the last digit of the year (0 to 9) M is the month (1 to 9, O, N, or D) D is a period of days: 1 – 1st to 10th 2 – 11th to 20th 3 – 21st to 31st Sanken Control Number SANKEN ELECTRIC CO., LTD. 3 Electrical Characteristics • Refer to the datasheet for details. • The polarity value for current specifies a sink as "+ ," and a source as “−,” referencing the IC. Absolute Maximum Ratings Unless specifically noted, TA is 25°C Characteristic VCC Pin Voltage VINS Pin Voltage Symbol Pins Rating Unit VCC 7–1 –0.3 to 30 V VINS 4–1 –0.3 to 5.5 V VICOMP 2–1 –0.3 to 5.5 V IS Pin Voltage VIS 3–1 –5.5 to 0.3 V IS Pin Current IIS 3–1 –1 to 1 mA VFB Pin Voltage VFB 6–1 –0.3 to 5.5 V VFB Pin Current IFB 6–1 –1 to 1 mA ICOMP Pin Voltage VCOMP Pin Voltage VVCOMP 5–1 –0.3 to 5.5 V GATE Pin Voltage VGATE 8–1 –0.3 to 30 V Frame Temperature during Operation TFOP – –40 to 110 °C Storage Temperature Tstg – –40 to 125 °C Junction Temperature TJ – –40 to 150 °C SSC2001S-AN, Rev.1.2 SANKEN ELECTRIC CO., LTD. 4 Electrical Characteristics of Control Part Unless specifically noted, TA is 25°C, VCC = 15 V Characteristic Symbol Test Conditions Pins Min. Typ. Max. Unit Power Supply Startup Operation Operation Start Voltage VCC(ON) 7–1 10.5 11.3 12.1 V Operation Stop Voltage VCC(OFF) 7–1 9.5 10.3 11.1 V Operation Voltage Hysteresis VCC(HYS) 7–1 0.7 0.9 1.1 V Circuit Current in Non-Operation ICC(OFF) 7–1 30 100 200 μA 7–1 6.0 9.0 12.0 mA 7–1 2.0 4.0 6.0 mA Circuit Current in Operation Circuit Current in Standby VCC = 10 V ICC(ON) ICC(STANDBY) VFB = 0.5 V Oscillation Operation Operation Frequency fOSC VIS = 0 V, VVCOMP = 4 V 8–1 57 65 70 kHz Maximum Duty Cycle DMAX VIS = 0 V, VVCOMP = 4 V 8–1 90 94 99.3 % DMIN VIS = 0.5 V, VVCOMP = 0 V Minimum Duty Cycle 8–1 – – 0 % tOFFMIN 8–1 150 250 350 ns VFB Pin Open Loop Detection Threshold Voltage VFB(OLD) 6–1 0.51 0.55 0.59 V VFB Pin Overvoltage Protection Threshold Voltage VFB(OVP) 6–1 3.57 3.745 3.85 V IS Pin Overcurrent Protection High Threshold Voltage VIS(OCPH) 3–1 −0.81 −0.75 −0.69 V IS Pin Overcurrent Protection Low Threshold Voltage VIS(OCPL) 3–1 −0.54 −0.5 −0.46 V VINS Pin Input Undervoltage Protection Low Threshold Voltage VINS(L) 4–1 0.51 0.55 0.59 V VINS Pin Input Undervoltage Protection High Threshold Voltage VINS(H) 4–1 0.94 1.0 1.08 V IVINS(BIAS) 4–1 −1.0 − 0 μA Current Amplifier Transconductance Gain gmCA – 1.1 1.4 1.7 mS Current Amplifier Output Source Current* ICA(SO) – – −50 – μA Current Amplifier Output Sink Current* ICA(SK) – – 50 – μA 2–1 3.6 4.0 4.3 V 6–1 3.4 3.5 3.6 V Minimum Off-Time* Protection Operation VINS Pin Input Undervoltage Protection Bias Current VVINS = 0 V Current Loop ICOMP Pin Output Open Loop Detection Threshold Voltage VICOMP(OLD) VFB = 0.5 V Voltage Loop Error Amplifier Reference Voltage VFB(REF) Error Amplifier Transconductance Gain gmEA – 45 60 75 μS Error Amplifier Maximum Source Current IVCOMP(SO) 5–1 −38 −30 −21 μA Error Amplifier Maximum Sink Current IVCOMP(SK) 5–1 21 30 38 μA IVCOMP = 0 μA Continued on the next page… SSC2001S-AN, Rev.1.2 SANKEN ELECTRIC CO., LTD. 5 Electrical Characteristics of Control Part (continued) Unless specifically noted, TA is 25°C, VCC = 15 V Characteristic Symbol Test Conditions Pins Min. Typ. Max. Unit Voltage Loop (continued) VFB Pin High Speed Load Response Operation Enable Voltage* VFB(HSR)ENABLE 6–1 – 3.4 – V VFB Pin High Speed Load Response Operation Start Voltage VFB(HSR)ACTIVE 6–1 3.24 3.325 3.41 V VCOMP Pin High Speed Load Response Source Current IVCOMP(SOHSR) 5–1 −127 −100 −72 μA IFB(BIAS) 6–1 – – 1 μA 5–1 0.60 1.03 1.40 V VFB Pin Input Bias Current VCOMP Pin Output Open Loop Detection Threshold Voltage VVCOMP(OLD) VFB = 0.5 V Drive Circuit GATE Pin Voltage (Low) VGATE(L) IGATE = −20 mA 8–1 – – 0.4 V GATE Pin Voltage (High) VGATE(H) VCC = 11 V 8–1 – 10.5 – V GATE Pin Rise Time tr 8–1 – 100 – ns GATE Pin Fall Time tf 8–1 – 50 – ns GATE Pin Peak Source Current* IGATE(SO) 8–1 – −0.5 – A GATE Pin Peak Sink Current* IGATE(SK) 8–1 – 1.0 – A – − 65 85 °C /W Thermal Resistance from Junction to Frame RθJ-F The frame temperature, TF , is specified by using the temperature at the base of pin 1. *Determined by design, not tested in production. SSC2001S-AN, Rev.1.2 SANKEN ELECTRIC CO., LTD. 6 Typical Application Circuit D2 VAC Input 入力 ﾌｨﾙﾀｰ filter E IN D1 L1 C1 C2 R8 Q1 R9 R1 R2 1 2 R3 3 SSC2001S GND GATE ICOMP VCC IS VFB 4 VI NS VCOMP R4 GND 8 External power supply 7 DZ1 C3 U1 SANKEN ELECTRIC CO., LTD. R6 6 5 R5 C8 C4 SSC2001S-AN, Rev.1.2 VOUT C5 C7 R7 C6 7 Functional Description With regard to current direction, "+" indicates sink current (toward the IC) and "–" indicates source current (from the IC). D2 VAC Startup Operation Figure 1 shows the VCC pin peripheral circuit. The VCC pin is the control circuit power supply input to supply voltage from the external power supply. The control voltage range of the VCC pin is wide: from VCC(OFF) of 11.1 V (max) to the maximum rating of 30 V (max). This permits a very wide value range for the external power supply voltage. VOUT D1 R8 C1 C2 Q1 R9 R1 As shown in figure 2, when VCC pin voltage rises to the operation start voltage, VCC (ON) , of 11.3 V (typ), the control circuit starts operation. When VCC drops to the operation stop voltage, VCC(OFF) , of 10.3 V (typ), the control circuit stops operation by the UVLO (undervoltage lockout) circuit, and reverts to the state before startup. L1 EIN GATE 8 1 GND R3 GND 2 ICOMP VCC 7 3 IS VFB 6 External 外部電源 power supply 4 VINS VCOMP 5 R4 C4 U1 R7 C7 Cf R6 C8 Figure 1. VCC pin peripheral circuit When the distance between the IC and the electrolytic capacitor C8 is long, a film capacitor Cf (approximately 0.1 μF) should be added between the VCC pin and the GND pin. After the input voltage at startup of the power supply meets the following conditions, and the VCC pin voltage reaches VCC (ON) , the soft start function starts operation (as described in the Soft Start Function section): ICC ICC(ON) 9 mA(typ) Start-up • VFB pin voltage > Output open loop detection voltage VFB(OLD) = 0.55 V (typ); VFB(OLD) = 0.55 V (typ) is equivalent to 16% of the error amplifier reference voltage VFB(REF) = 3.5 V (typ) (refer to the Output Open Loop Detection (OLD) section) Stop • VINS pin voltage > Input Undervoltage Protection High Threshold Voltage, VINS(H) = 1.0 V (typ) (refer the Brown-In/BrownOut Function section) ICC(OFF) 100 μA(typ) 10.3 V(typ) VCC(OFF) 11.3 V(typ) VCC(ON) VCC Figure 2. VCC versus ICC SSC2001S-AN, Rev.1.2 SANKEN ELECTRIC CO., LTD. 8 Soft Start Function When the input voltage meets the power supply startup conditions (refer to the Startup Operation section) and the VCC pin voltage reaches the VCC(ON) voltage, the power supply enters soft start operation. The continuity of inductor current depends on the value of inductance. During light loads, the operation is in DCM, but the requirement of the class D of IEC1000-3-2 for harmonic currents can be met. During soft start, the VCOMP pin is charged by the error amplifier maximum source current IVCOMP(SO) = –30 μA (typ) until the VFB pin voltage becomes approximately 3 V, which is approximately 85% of output voltage setting, and then power is gradually increased to reduce the stress on component parts. By means of CCM in the operation of the IC series, the usual requirement for a multiplier to transform the input current into a sinusoidal waveform, as well as the related components for the detection of the input voltage, are no more required. This results in a reduction of external parts and simple circuit configurations. Continuous Conduction Mode (CCM) Operation When the inductor current of the PFC circuit is in a continuous state, continuous conduction mode (CCM) operation is occurring. In CCM, the peak inductor current becomes low compared to the peak during discontinuous conduction mode (DCM), at the same output power (refer to figures 3 and 4). This allows a reduction in the rated current of the boosting power MOSFET and a decrease of loss to RDS(ON) . This characteristic is suitable for high output power. For the off duty cycle, DOFF , of the booster system, the input voltage, VIN , and the output voltage, VOUT , have the relationship of DOFF = VIN / VOUT and so the off-time is proportional to VIN . The IC generates a sinusoidal waveform for input current and constant output voltage, by means of duty cycle control, which combines current control and voltage control. AC Input Voltage Inductor Current Average Inductor Current MOSFET Drain Current, ID Superimposed DC Inductor Current Inductor Current, IL Gate Output Continuous Conduction Mode (CCM) Discontinuous Conduction Mode (DCM) Figure 3. Current waveforms in continuous and discontinuous conduction modes SSC2001S-AN, Rev.1.2 Figure 4. Inductor current in continuous conduction mode SANKEN ELECTRIC CO., LTD. 9 When VOUT decreases due to increased load, the VCOMP pin voltage is increased, making the slope of the ramp waveform steeper, and the output power is increased by raising the duty cycle. Current Control (PFC Control) Figure 5 shows a typical peripheral circuit for the IC. The inductor current, IL , is detected at the detection resistor, R1, and input into the IS pin to be averaged at capacitor C3 (on the ICOMP pin) via the current amplifier in the IC so that the ICOMP pin voltage is produced in proportion to the inductor average current. In order to boost the input voltage at the AC mains frequency, voltage control is generally activated in response to 20 Hz or lower against AC mains frequency. As shown in figure 6, the input current is controlled to be sinusoidal by comparing the ICOMP pin voltage with the waveform of a ramp generator in the IC. In standby mode or at the operation of a protection circuit, the ICOMP pin voltage is clamped at 4 V (typ) in the IC. The reference value of R6 is several hundred kilohms to several megohms. Because of high voltage applied and high resistance value, it is recommended to select a resistor designed against electromigration or use a combination of resistors for that. The C3 value has a filtering effect on the switching frequency and the ripple voltage of the inductor current. IL . The time constant should be set so as to be subjected to the AC mains frequency. Slope affected by VCOMP voltage VICOMP The reference value of C3 is from 1 to 22 nF, and it should be adjusted so that the AC input current becomes sinusoidal, while varying loads in actual operation in the application. Ramp waveform PWM Voltage Control (Output Constant Voltage Control) The VFB pin voltage, which is the value of the output voltage, VOUT , divided by R6 and R7 in figure 5, is compared to the reference voltage, VFB(REF) = 3.5 V (typ) by the error amplifier in the IC. This result is output to the VCOMP pin. The VCOMP pin voltage, which is added compensation values by C5, C6, and R5, adjusts the slope of the ramp waveform shown in figure 6, so that VOUT is controlled constant. Off tOFF(min) 250 ns (typ) On fSW Ramp waveform reset Figure 6. Internal ramp function waveform D2 VAC L1 EIN D1 C1 R8 Inductor Current, IL VOUT C2 Q1 R9 GND R1 R6 R2 R4 C4 GATE 8 1 GND R3 2 ICOMP VCC 7 3 IS VFB 6 4 VINS VCOMP 5 DZ1 C3 External Power Supply U1 R5 C8 C5 C7 R7 C6 Figure 5. IC peripheral circuits SSC2001S-AN, Rev.1.2 SANKEN ELECTRIC CO., LTD. 10 The reference value of C7 is from 0.047 to 0.1 μF for high frequency noise reduction. The reference value of C5 is from 0.047 to 0.47 μF, that of C6 is 0.47 to 10 μF, and that of R5 is 10 to 47 kΩ. The values should be adjusted under actual operation in the application in order to decrease ripple on the output voltage, VOUT , waveform. High Speed Load Response (HSR) Because the AC mains input voltage and frequency are used for the PFC of the boost system, voltage control is activated in response to low mains frequency, and as a result the dynamic load response is slow and a decrease of output voltage, VOUT , is likely to occur. In order to suppress the variation in VOUT at the time of dynamic load conditions, the high speed load response function (HSR) is built in to the IC. As shown in figure 7, the high speed load response function (HSR) is enabled when the VFB pin voltage exceeds the high speed load response operation enabling voltage, VFB(HSR)ENABLE = 3.4 V (typ). Later, when VOUT decreases due to dynamic load response below the high speed load response operation start voltage, VFB(HSR)ACTIVE = 3.325 V (typ), the HSR becomes active and the VCOMP pin is charged by the high speed load response source current IVCOMP(SOHSR) = –100 μA (typ) until the VFB pin voltage increases to VFB(HSR)ACTIVE. This increases the output power and suppresses the decrease of VOUT . VFB(HSR)ACTIVE = 3.325 V (typ) is 95% of the error amplifier reference voltage VFB(REF) = 3.5 V (typ) set by the output voltage, VOUT . Frequency Modulation The built-in frequency modulation function references an internally generated fixed operation frequency, fOSC = 65 kHz (typ). It superimposes a variable frequency which modulates at a rate based on the output duty cycle. The modulation frequency is low when the duty cycle is large (input voltage is low), and the modulation frequency is high when the duty cycle is small (input voltage is high). The second harmonic frequency after modulation keeps less than 150 kHz. Gate Drive The peak source current /peak sink current of the GATE pin are set at –0.5 A (typ) / 1.0 A (typ), and the low voltage /high voltage are set at 0.4 V (max) / 10.5 V (typ) for directly driving the power MOSFET. Peripheral component values of the GATE pin in figure 8 are affected by the printed circuit board trace layout and the power MOSFET capacitance, which should be adjusted under actual operation of the application. R8 is adjusted to decrease ringing of GATE pin voltage and EMI noise. The reference value of R8 is several ohms to several dozen ohms. R9 is used to prevent malfunctions due to steep dv / dt at turn-off of the power MOSFET, and the resistor is connected near the MOSFET, between the gate and source. The reference value of R9 is from 10 to 100 kΩ. Gate output off VFB Pin Voltage 3. 745V HSR active HSR off HSR enable L1 3. 5 V D1 Q1 R8 3. 4 V 3. 325V ≈3 V R9 HSR 1 GND SS CV LC CV OV CV SSC2001S-AN, Rev.1.2 2 ICOMP VCC 7 3 IS VFB 6 4 VINS VCOMP 5 CV – Steady operation period HSR – High speed load response operation period LC – Dynamic load variation period OV – Overvoltage operation period SS – Soft start period Figure 7. VFB pin voltage GATE 8 U1 Figure 8. GATE pin peripheral circuit SANKEN ELECTRIC CO., LTD. 11 Protection Functions Overcurrent Protection (OCP) As shown in figure 9, the inductor current, IL , is detected at the detection resistor R1 and input into the current amplifier in the IC via the IS pin. The overcurrent protection operation (OCP) has the following two states: Brown-In / Brown-Out The brown-in/brown-out function prevents switching operation while input voltage is low. This protects against exceeding input current ratings and overheating the IC and the power supply. 1. IS pin overcurrent protection (low), VIS(OCPL) As shown in figure 1, the VINS pin voltage is the value of the input voltage VIN divided by R3 and R4. When the VINS pin voltage is at the input undervoltage protection high threshold voltage, VINS(H) =1.0V (typ), or more, the control circuit is allowed to operate. When the VINS pin voltage is at the input undervoltage protection low threshold voltage, VINS(L) = 0.55 V (typ), or less, the control circuit stops switching oscillation, and the IC enters standby mode. This is the first level of OCP. When the IS pin voltage is at the overcurrent protection low threshold voltage, VIS(OCPL) = –0.5 V (typ), or less, the duty cycle is reduced at the next cycle to restrict the input power. The value of detection resistor R1 is adjusted in a manner that the IS pin does not go below VIS(OCPL) at the lower limit of input voltage and peak load. The value of R2 is 220 Ω resistance, to maintain the IS pin current within ±1 mA during surges such as in-rush current. DZ1 is 4.7 V Zener diode connected for protection against any overvoltage applied. R3 is usually several megohms. Because of high voltage applied and high resistance value, it is recommended to select a resistor designed against electromigration or a combination of resistors for that. C4 is used to decrease the ripple on the detected voltage and to set the delay time, and the reference value is from 0.047 to 1 μF. 2. IS pin overcurrent protection (high), VIS(OCPH) If using remote on/off control of the PFC function, to remotely implement the off state, the voltage at the VINS pin should be VINS(L) or less. It should be noted that during the previous remote-off control, power consumption occurs by ICC(STANDBY) = 4 mA (typ). In order to minimize power consumption during remote-off, the following methods are recommended: to turn off the external power supply on the VCC pin, or turn off an external switch inserted on power source line to the VCC pin. VAC This is the second level of OCP. When the IS pin voltage is at the overcurrent protection high threshold voltage, VIS(OCPH) = –0.75 V (typ), or less, the gate output is turned off using pulseby-pulse basis. When the cause of the overcurrent is removed, the IC returns to normal operation automatically. In order to prevent malfunction due to noise, a leading edge blanking period of 300 ns is built in. L1 EIN C1 D1 R8 Inductor Current, IL Q1 R9 C2 GND R1 R2 VOUT GATE 8 1 GND 2 ICOMP VCC 7 3 IS VFB 6 4 VINS VCOMP 5 DZ1 C3 U1 Figure 9. IS pin peripheral circuit SSC2001S-AN, Rev.1.2 SANKEN ELECTRIC CO., LTD. 12 Output Overvoltage Protection (OVP) When the VFB pin voltage exceeds the output overvoltage protection threshold voltage, VFB(OVP) = 3.745 V (typ), the gate output is turned off using pulse-by-pulse basis. When the cause of the overvoltage is removed, the IC returns to normal operation automatically. VFB(OVP) = 3.745 V (typ) is equivalent to 107% of the error amplifier reference voltage VFB(REF) = 3.5 V (typ) for output voltage VOUT setting. Output Open Loop Detection (OLD) As a protection against open loop of the output voltage, when the VFB pin voltage is at the output open loop detection threshold voltage, VFB(OLD) = 0.55V (typ), or less, the control circuit stops switching oscillation, and the IC enters standby mode. VFB(OLD) = 0.55 V (typ) is equivalent to 16% of the error amplifier reference voltage, VFB(REF) = 3.5 V (typ) for output voltage VOUT setting. When the cause of the open loop is removed, the IC returns to normal operation automatically. When this protection function is activated, the VCOMP pin is clamped to 1.03 V (typ) in the IC. D1 VOUT C2 GND U1 1 GND R6 GATE 8 2 ICOMP VCC 7 3 IS VFB 6 R5 4 VINS VCOMP 5 C5 C7 R7 C6 Figure 10. VFB pin peripheral circuit SSC2001S-AN, Rev.1.2 SANKEN ELECTRIC CO., LTD. 13 Design Notes 1. Output voltage VOUT setting for boost converter Inductor Design Parameters The following abbreviations are used in this description: Given the relationship of input voltage < output voltage, set the voltage of VOUT higher than the peak value of the AC input voltage by approximately 10 V, according to the following equation: PIN – PFC input power (W) (1) VOUT > 2 VINRMS(max) + 10 (V) PO – PFC output power (W) 2. Inductor current setting η – Efficiency of PFC section (reference value: 0.92) As shown in figure 12, the inductor ripple current is superimposed on the input current, IIN . VINRMS – Input voltage rms (root mean square) value (V) VOUT – Output voltage (V) IINRMS – Input current rms value (A) IOUT – Output current (A), PO / VOUT Average Inductor Current, IINRMS Inductor Ripple Current, ILRIPPLE DON – Duty cycle, ( VOUT – √2 VINRMS ) / VOUT ILRIPPLE /2 ILPEAK(max) DOFF – Off-portion of duty cycle, √2 VINRMS / VOUT fSW – Switching frequency, 65 kHz (typ) IINPEAK(max) ILRIPPLE fAC – AC mains frequency (Hz) r – Ratio of ripple current to maximum peak input current, ILRIPPLE/IINPEAK(max) Figure 12. Inductor current D2 VAC Input Filter L1 D1 R8 Inductor Current, IL Q1 VOUT C2 R9 GND R1 U1 R2 1 GND R6 GATE 8 2 ICOMP VCC 7 3 IS VFB 6 4 VINS VCOMP 5 R7 Figure 11. Boost converter circuit SSC2001S-AN, Rev.1.2 SANKEN ELECTRIC CO., LTD. 14 The inductor maximum peak current ILPEAK(max) is obtained by the following steps. overcurrent protection: ILOCP(max) The maximum input current rms value IINRMS(max) is: IINRMS(max) = POUT(max) H × VINRMS(min) (2) (A) The maximum input current peak value IINPEAK(max) is: IINPEAK(max) = 2 IINRMS(max) (3) (A) The inductor maximum current peak value ILPEAK(max) is: r ILPEAK(max) = IINPEAK(max) 1+ (A) (4) 2 In consideration of inductor size and the extent of superimposed ripple current, the ripple ratio, r, is generally 15% to 40%. L1 r × (VOUT – 2VINRMS(min)) (H) The capacitance, CO , of C2 is selected using either of the following two methods, whichever yields the larger value: 6a. Ripple voltage When the ripple voltage of C2 is expressed as peak-to-peak VOUTRIPPLE, for example, 10 Vpp , the following equation is obtained: R1 is obtained from the IS pin overcurrent protection low threshold value VIS(OCPL) and the inductor maximum peak current ILPEAK(max) for the first level of overcurrent protection, as shown in the following equation: ILPEAK(max) (Ω) (6) 5. Current limiting value ILOCP(MAX) at overcurrent operation ILOCP(max) is obtained from IS pin overcurrent protection high threshold value VIS(OCPH) and R1 for the second level of SSC2001S-AN, Rev.1.2 IOUT 2 fAC × VOUTRIPPLE (8) (F) VOUT ±VOUTRIPPLE /2 (5) 4. Overcurrent detection resistor R1 |VIS(OCPL)| (7) In addition, the voltage of C2 will be: r × fSW × PIN × VOUT R1 r (A) 6. Output capacitor C2 capacitance CO r 2 VINRMS(min) R1 When the IS pin overcurrent protection high threshold is activated, the gate output is turned off using pulse-by-pulse basis. The inductor must be designed to accommodate the power supply operation at overcurrent levels. 3. Inductance value The inductance can be calculated as: |VIS(OCPH)| (9) When this voltage exceeds the output overvoltage protection detection voltage (VOUT × 1. 07), or falls below the peak value of the input voltage, boost operation is stopped and the input waveform may eventually be distorted. If the distortion is significant, it is necessary to make CO larger or alter the output voltage setting value (boost voltage value). 6b. Output holding time When the minimum input voltage of C2 at the output holding time, tHOLD , is expressed as VOUT(min), the following equation is obtained: CO SANKEN ELECTRIC CO., LTD. 2 × POUT × tHOLD 2 (VOUT – 2 VOUT (min)) × (F) (10) 15 Peripheral Components Take care to use the proper rating and proper type of components. For circuit symbols please refer to figure 13. • The electrolytic capacitor C2 should have some margin for ripple current/voltage and temperature rise. High ripple and low impedance type parts for switch-mode power supplies should be used. • The inductor L1 should have some margin for temperature rise due to core loss and copper loss. • Because high frequency switching current flows across the current detection resistor R1, the use of a resistor with large internal inductance may cause malfunctions. A resistor with small inductance and high surge tolerance should be used. • The resistors such as R3 and R6, which have applied high voltage and have high resistance values, should be selected from resistors designed against electromigration or use a combination of resistors for that. • D2 is a bypass diode which protects D1 against overcurrents, such as in-rush current. Therefore a diode with high surge tolerance is recommended. • For D1, an ultra high speed diode with short reverse recovery time, trr , is recommended to decrease noise and loss. • With respect to the product lineup of rectifier and bypass diodes, please contact our sales division. + U1 External power supply Main circuit Control system GND circuit Figure 13. Example of connection of peripheral components SSC2001S-AN, Rev.1.2 SANKEN ELECTRIC CO., LTD. 16 PCB Trace Layout and Component Placement PCB circuit trace design and component layout significantly affect operation, EMI noise, and power dissipation. Therefore, pay extra attention to these designs. In general, where high frequency current traces form a loop, as shown in figure 14, wide, short traces, and small circuit loops are important to reduce line impedance. In addition, earth ground traces affect radiated EMI noise, and the same measures should be taken into account. • The control circuit traces should not be placed in parallel with the main circuit traces in order not to pick up crosstalk noise. Switch-mode power supplies consist of current traces with high frequency and high voltage, and thus trace design and component layouts should be done to comply with all safety guidelines. • Peripheral circuit components should be connected to the IC by using the shortest traces possible. • In order to minimize the common impedance of the control ground circuit and main circuit ground, the GND pin (pin 1) trace should be connected at the pin of R1 by a dedicated trace, using the shortest trace possible. The R2 trace also should be connected at the pin of R1 in a similar way. Furthermore, because the incorporated power MOSFET has a positive thermal coefficient of RDS(ON), consider it when preparing a thermal design. • If the VCC pin and electrolytic capacitor C8 are distant from each other, placing a capacitor (approximately 0.1 to 1.0 μF film capacitor) close to the VCC pin and the GND pin is recommended. Figure 13 shows a circuit layout design example. • R9 must be connected to the gate pin and source pin of Q1. D2 VOUT D1 L1 Q1 C2 C1 GND R1 Figure 14. High frequency current loops (hatched areas) SSC2001S-AN, Rev.1.2 SANKEN ELECTRIC CO., LTD. 17 • The contents in this document are subject to changes, for improvement and other purposes, without notice. Make sure that this is the latest revision of the document before use. • Application and operation examples described in this document are quoted for the sole purpose of reference for the use of the products herein and Sanken can assume no responsibility for any infringement of industrial property rights, intellectual property rights or any other rights of Sanken or any third party which may result from its use. • Although Sanken undertakes to enhance the quality and reliability of its products, the occurrence of failure and defect of semiconductor products at a certain rate is inevitable. Users of Sanken products are requested to take, at their own risk, preventative measures including safety design of the equipment or systems against any possible injury, death, fires or damages to the society due to device failure or malfunction. • Sanken products listed in this document are designed and intended for the use as components in general purpose electronic equipment or apparatus (home appliances, office equipment, telecommunication equipment, measuring equipment, etc.). When considering the use of Sanken products in the applications where higher reliability is required (transportation equipment and its control systems, traffic signal control systems or equipment, fire/crime alarm systems, various safety devices, etc.), and whenever long life expectancy is required even in general purpose electronic equipment or apparatus, please contact your nearest Sanken sales representative to discuss, prior to the use of the products herein. The use of Sanken products without the written consent of Sanken in the applications where extremely high reliability is required (aerospace equipment, nuclear power control systems, life support systems, etc.) is strictly prohibited. • In the case that you use Sanken products or design your products by using Sanken products, the reliability largely depends on the degree of derating to be made to the rated values. Derating may be interpreted as a case that an operation range is set by derating the load from each rated value or surge voltage or noise is considered for derating in order to assure or improve the reliability. In general, derating factors include electric stresses such as electric voltage, electric current, electric power etc., environmental stresses such as ambient temperature, humidity etc. and thermal stress caused due to self-heating of semiconductor products. For these stresses, instantaneous values, maximum values and minimum values must be taken into consideration. In addition, it should be noted that since power devices or IC's including power devices have large self-heating value, the degree of derating of junction temperature affects the reliability significantly. • When using the products specified herein by either (i) combining other products or materials therewith or (ii) physically, chemically or otherwise processing or treating the products, please duly consider all possible risks that may result from all such uses in advance and proceed therewith at your own responsibility. • Anti radioactive ray design is not considered for the products listed herein. • Sanken assumes no responsibility for any troubles, such as dropping products caused during transportation out of Sanken's distribution network. • The contents in this document must not be transcribed or copied without Sanken's written consent. SSC2001S-AN, Rev.1.2 SANKEN ELECTRIC CO., LTD. 18